Cutting tool for honeycomb core

Abstract: A cutting tool for cutting a honeycomb core has a plurality of spiral blades (3) each of which is formed integrally with a cylindrical body (2) of the cutting tool and has a lead angle (γ) of 60 degrees or more with respect to an axis of the cylindrical body (2). Each of the blades (3) comprises a radial edge (4) with a lip angle (α) ranging from 1 degree to 20 degrees along the periphery of the cutting tool and a bottom edge (5) with a lip angle (β) ranging from 1 degree to 20 degrees at the bottom of the cutting tool. The bottom edge (5) is curved outward in the revolutional direction of the blade.

Description: The present invention relates to a cutting tool for cutting honeycomb cores. A commonly used cutting tool for cutting honeycomb cores has a valve stem shaped cutter (hereinafter referred to as "valve stem cutter") having a sharp cutting edge like a razor blade built along the periphery of a conical disk. Since this valve stem cutter has no kerf on the cutting edge, it keeps in a linear contact with a workpiece during cutting and consequently this type of cutter tends to become burned at the cutting edge due to frictional heat. Further, differently from usual cutting tools, since the valve stem cutter cuts a workpiece with a slitting or splitting action by continuously applying an edge laterally, a high rotational speed is required. However, on the other hand, the feed speed can not be raised sufficiently for the high rotational speed of the cutting tool and as a result in some cases it becomes difficult for this type of cutting tool to cut a plate having a honeycomb core, if the thickness of the plate is large. As an improved valve stem cutter, there is proposed a cutting tool for cutting a honeycomb core in which several splitting saws with a different diameter are coaxially heaped up so as to break tips produced from the splitting saws with a large diameter by the splitting saws with a small diameter (Japanese utility application laid open No. 1989-315). However, the cutting edge of this splitting type cutter is not as keen as a razor edge and therefore problems occur, eg. a large cutting resistance is applied on it, burrs tend to be produced on its cutting plane and a workpiece tends to be deposited on its cutting edge at high speed cuttings because it has a small chip pocket and a straight edge. On the other hand, as another type of cutting tool for a honeycomb core which is different from the above splitting type cutter, there is an intermittent cutting type of cutter. For example, as disclosed in Japanese Utility application published No. 1991-75922, there is a cutting tool having a disk-shaped cutter with a chip space and a radial relief angle at the cutting edge. The chip space of the disk-shaped cutter is integrally connected to the chip space of the chip breaker. Furthermore, in order to raise a bite-in characteristic and at the same time to reduce a cutting resistance, an axial rake angle is built in the disk-shaped cutter along the chip space twisted towards the right hand and additionally a positive radial rake angle is built both in the cutter and the chip breaker. This intermittent cutting type cutter also has disadvantages that surface finishing becomes poor and further that high precision cutting can not be performed efficiently because a work-holding of the honeycomb core on the machine tends to become unstable due to a vibrational force acting on the workpiece. In view of the foregoing problems and disadvantages, an object of the present invention is to provide a cutting tool which can cut a honeycomb core efficiently by reducing cutting resistance and preventing a cutting edge from being burned. Reference is also made to SU-946815, which discloses a rotary cutting tool for cutting a honeycomb core according to the preamble of claim 1. This tool has a cylindrical cutting head with a helical V-form groove in its surface, forming a cutting edge of constant helix angle. An elliptical lead-in to the cutting head is provided, to improve cutting productivity. In accordance with a first aspect of the present invention, there is provided a cutting tool for cutting a honeycomb core , comprising: a shank; a cylinder coaxially connected to said shank; and a circumferential cutting edge spirally and integrally formed on said cylinder; a bottom edge formed at a lower end of said circumferential cutting edge to initially bite in said honeycomb core ; and a boundary portion interposed between said circumferential cutting edge and said bottom edge to smoothly connect therebetween and to cut a boundary region of said honeycomb core ; and wherein: said circumferential cutting edge has a lead angle which is 60 degrees or greater with respect to the longitudinal axis of said cylinder; and lip angles of said circumferential cutting edge and said bottom edge are between 1 and 20 degrees; characterised in that: said circumferential cutting edge is formed by a plurality of blades; wherein each blade has a circumferential bevel inclined upwardly and outwardly relative to the tool axis, meeting an upper surface of the blade to form a circumferential cutting edge at the outermost part of the blade to continuously cut said honeycomb core. Using such a tool, the bottom edge cuts the honeycomb core with a width of cut approximately corresponding to a diameter of the cutting tool and the radial edge cuts the honeycomb core continuously by a splitting-scraping effect up to a depth corresponding to a vertical length of the radial edge, resulting in removal of material from the honeycomb core in the form of small chips or flakes. According to the present invention, the cutting tool has a plurality of spiral blades and each of the blades has a keen cutting edge with an extremely acute angle which comprises a radial edge portion and a bottom edge portion. A depth of cut is restricted by the vertical length of the radial edge portion and a width of cut is determined approximately by the bottom edge portion which corresponds to the diameter of the cutting tool. Observing one blade in the cutting tool, the cutting edge of the blade cuts an object by splitting and at the same time scraping, however viewing the whole of the cutting tool, it cuts the object intermittently. Namely, according to the cutting tool of the present invention, the cutting method by splitting and scraping reduces a cutting resistance and the intermittent cutting method prevents a cutting edge from being burned. As a result of this, a cutting process with a high rotational speed and a high feed speed can be obtained. By way of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawings, in which:- Fig. 1 is a side elevation showing the components constituting the cutting edge of a cutting tool for a honeycomb core, according to an embodiment of the present invention; Fig. 2 is a view for explaining a figure of the bottom edge of the cutting tool for a honeycomb core according to the embodiment of Fig. 1; Fig. 3 is a schematic view of the cutting edge portion of the embodiment of Fig. 1; Fig. 4 is a perspective view of the bottom edge of the cutting tool of Fig. 1; and Fig. 5 is a perspective view of the cutting process using the cutting tool of Fig. 1. Referring to Figs. 1 and 4, numeral 1 denotes a shank of the cutting tool according to the present invention. The shank 1 is connected to a cylinder 2 with a large diameter around which a plurality of spiral blades 3 are formed integrally together with the cylinder 2. In the illustrated embodiment of the present invention, the cutting tool comprises four blades. A ridgeline of the blade 3 is slanted with a lead angle τ of at least 60 degrees with respect to an axis of the shank. It is desirable that the lead angle τ ranges from 60 degrees to 85 degrees because the cutting effect by slitting and scraping can not be obtained with a lead angle τ below 60 degrees. Referring now to Fig. 3, a cutting edge forming the ridgeline of the blade 3 comprises a radial edge 4 which surrounds the cylinder 2 peripherally and a bottom edge 5 which is shaped at the bottom of the cylinder 2. The radial edge 4 is smoothly connected to the bottom edge 5 through a boundary portion 4a. The radial edge 4 is composed as follows. Referring to Fig. 1, a numeral α denotes a lip angle and a numeral Θ 1 represents a rake angle. In this preferred embodiment, it is desirable that the lip angle α should be an extremely acute angle, specifically 1 to 20 degrees. The lip angle less than 1 degree should be avoided from the view point of rigidity of the cutting edge. The rake angle Θ 1 is determined within a range of 20 degrees to -20 degrees according to the material of a honeycomb core to be processed and cutting conditions. On the other hand, referring to Fig. 2, an edge portion of the bottom edge 5 has a shape of sector or involute curved toward the rotational direction of the cutting tool. With respect to the bottom edge 5, a lip angle is represented by β and a relief angle by Θ 2 . In this preferred embodiment, the lip angle β should be within a range of 1 to 20 degrees, similarly to the lip angle of the radial edge 4. The relief angle Θ 2 is 2 degrees at the maximum. A radial rake angle Θ 3 of the bottom edge 5 is determined at a negative degree, aiming at a smooth cutting-in. To make the radial rake angle Θ 3 of the bottom edge 5 negative, the rake angle Θ 1 of the radial edge 4 near the bottom edge 5 is rendered negative. Thus, the radial rake angle Θ 3 can be made negative without any special processing applied. Fig. 5 is a view for showing the cutting work on a workpiece of the honeycomb core. The cutting tool is connected to the spindle of a machine (not shown) and it cuts the honeycomb core W in the lateral direction at a high revolutional speed, for example 12000 rpm and at a feed speed of the machine of, for example, 12000 mm/min. Since the spiral blade 3 of the cutting tool has a sharp cutting edge with an extremely acute lip angle at the radial edge 4 and the bottom edge 5, the radial edge 4 cuts the honeycomb core by a splitting-scraping effect up to a depth corresponding to a vertical length of the radial edge 4 and on the other hand the bottom edge 5 cuts the honeycomb core with a width of cut approximately corresponding to a diameter of the cutting tool. Therefore, it is understood that each of the blades cuts the workpiece by the splitting-scraping effect and this occurs intermittently. That is to say, the cutting method using a splitting-scraping effect together with an intermittent cutting enables the cutting tool to achieve a high rotation and high feed cutting. Further, since the blade 3 slants with a high lead angle τ more than 60 degrees and has a sharp cutting edge with an extremely acute lip angle both at the radial edge 4 and the bottom edge 5, the cutting resistance in the radial direction and in the feed direction can be reduced when the honeycomb core is cut at high speeds. This reduced cutting resistance and the above intermittent cutting effect prevent the cutting tool from being burned and consequently provides it with a long life. Also, with regard to the surface finish, the same finish as in the case of a prior valve stem cutter can be obtained. Further, according to the cutting tool of the present invention, chips come off from the cutting tool easily because chips are produced in the shape of small chips or flakes by the effect of splitting and scraping of the radial edge 4 and the bite-in effect of the bottom edge 5. Further, according to an embodiment of the present invention, since the radial rake angle Θ 3 of the bottom edge 5 is designed to be negative, the cutting tool can bite the workpiece smoothly. In summary, the present invention provides a cutting tool capable of cutting with a high speed (high efficiency) by employing a splitting-scraping effect together with an intermittent cutting method and capable of elongating tool life by reducing the cutting resistance. Further, since the shape and size of chips are like small chips or small flakes, it becomes more easy to remove chips. Thus, the cutting tool according to the present invention will contribute a high efficiency to the cutting process of the honeycomb core. While the presently preferred embodiment of the present invention has been shown and described, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made within the scope of the claims.

Claims: A cutting tool for cutting a honeycomb core (W), comprising: a shank (1); a cylinder (2) coaxially connected to said shank (1); and a circumferential cutting edge (4) spirally and integrally formed on said cylinder (2); a bottom edge (5) formed at a lower end of said circumferential cutting edge (4) to initially bite in said honeycomb core (W); and a boundary portion (4a) interposed between said circumferential cutting edge (4) and said bottom edge (5) to smoothly connect therebetween and to cut a boundary region of said honeycomb core (W); and wherein: said circumferential cutting edge (4) has a lead angle (τ) which is 60 degrees or greater with respect to the longitudinal axis of said cylinder (2); and lip angles (α, β) of said circumferential cutting edge (4) and said bottom edge (5) are between 1 and 20 degrees, characterised in that: said circumferential cutting edge is formed by a plurality of blades (3); wherein each blade has a circumferential bevel inclined upwardly and outwardly relative to the tool axis, meeting an upper surface of the blade to form a circumferential cutting edge (4) at the outermost part of the blade to continuously cut said honeycomb core (W). A cutting tool as claimed in claim 1, wherein one end of said bottom edge (5) is connected to said cylinder (2) on a bottom face of said cylinder. A cutting tool as claimed in claim 1 or claim 2, wherein one end of said bottom edge (5) is connected to said cylinder (2) on a circumferential surface of said cylinder. A cutting tool as claimed in any of claims 1 to 3, wherein said circumferential cutting edge (4), said bottom edge (5) and said boundary portion (4a) are formed integrally and continuously on said blade so as to reduce cutting resistance. A cutting tool as claimed in any of claims 1 to 4, wherein an edge line of said bottom edge (5) is curved outward in a revolutional direction of said cutting tool. A cutting tool as claimed in any of claims 1 to 5, wherein a radial rake angle ( 3 ) of said bottom edge (5) is negative so as to reduce cutting resistance. A cutting tool as claimed in any preceding claim, wherein the bottom edge (5) cuts the honeycomb core with a width of cut approximately corresponding to a diameter of the cutting tool and the radial edge (4) cuts the honeycomb core continuously by a splitting-scraping effect up to a depth corresponding to a vertical length of the radial edge, resulting in removal of material from the honeycomb core in the form of small chips or flakes.

Inventors: OGAWA RYUICHI, OGAWA, RYUICHI
Applicants: FUJI HEAVY IND LTD, FUJI JUKOGYO KABUSHIKI KAISHA
Application year: 1994
Main classification: B23C5
IPC codes: B23C5